Final answer:
A chromosome is a structure inside a cell's nucleus, made of coiled DNA and proteins, that contains genetic information. It is visible during cell division and has specific identification features like banding patterns and centromere positions. The term 'chromosome' derives from the Greek words for color and body due to its staining properties.
Step-by-step explanation:
The chromosome is a threadlike structure within the nucleus of a cell, composed of DNA and proteins, which houses the genetic information of an organism. The DNA is coiled around proteins known as histones to form a substance called chromatin. During cell division, the chromatin coils more tightly to create the distinct, visible structures we refer to as chromosomes. These structures are crucial for the sorting and movement of genetic information as cells divide and are characterized by their banding patterns, size, the position of the centromere, and chromosome number, which is specific to each species.
For example, humans have 46 chromosomes, whereas fruit flies have only eight. The chromosomes can be stained to produce characteristic banding patterns, aiding in their identification under a microscope, much like miniature barcodes. This feature of chromosomes absorbing dyes led to their name, which comes from the Greek words for color (chroma) and body (soma).